This research addresses an important public need, the protection of an approximate 5-10 percent of the U.S. workforce who use their voice as a primary tool of trade. Evidence has been growing that occupational voice users, such as teachers, interviewers, counselors, and telephone workers, are at risk for vocal injury because they get inadequate recovery times from prolonged speaking. The underlying hypothesis of our research is that there is a limited vibration dose that vocal fold tissues can absorb. As to hand vibration transmitted by power tools, a safe dose is governed by frequency, tissue acceleration, and duration of exposure. We propose to design and test a dosimeter that measures these governing variables in vocalization, both in a controlled laboratory setting and on the job. We also propose to relate this vibration dose, and recovery times for the dose, to auto-perception of vocal fatigue. Since auto-perception requires little sophisticated instrumentation, we anticipate that a self-monitoring strategy will eventually evolve for all occupational voice users. Voice-economy oriented therapy will be administered to a group of teachers and compared to electronic amplification in its ability to prevent fatigue. The voice- economy therapy is driven by energy conservation principles, derived theoretically on computer simulation models of phonation, as well as by clinically accepted techniques that have withstood a test of time and are used currently by vocal performers. Specific aims are to (1) design and construct the dosimeter, (2) to measure the daily and weekly dose received by approximately 120 teachers on the job, (3) to provide a voice-economy oriented therapy program to a subset of about 60 of these, (4) to relate vibration dose at the larynx to vocal output, (5) to relate auto- perceptive measures of recovery time to vocal fatigue, short term rest periods and tissue health, and 6) to provide amplification to another subset of 20 teachers who are in a classroom setting. The Wilbur James Gould Voice Research Center, a division of the Denver Center for the Performing Arts, is well suited to conduct this study because it already has an active outreach program to the public schools and the business sector. It also has a residency theatre company.